Pavlinov I.Ya. (ed.) Research in Biodiversity

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Towards a Better Understanding of Beta Diversity: Deconstructing

Composition Patterns of Saproxylic Beetles Breeding in Recently Burnt Boreal Forest

Fig. 4. A two-dimensional MDS representation of site-to-site dissimilarity showing the effect

of tree species (a-c), burn severity (d-f) and tree-size class (g-i) on saproxylic beetle’s total

beta diversity(a,d,g), and when partitioned into “spatial” turnover (b,e,h) and nestedness-

driven (c,f,i) components. The ellipse encloses 80% of the dispersion of habitat classes from

their respective group centroid as accounted by the first two axes. Habitat classes are Tree

species: BSP=Black spruce and JPI=Jack pine; Burn severity: L=Low, M=Moderate and

H=High; Tree size/dbh (diameter at breast height in cm) classes: db1=8-12, db2=12-16,

db3=16-20 and db4=20-24.

The nestedness-driven beta diversity (β

nes

), however, was influenced by gradients of burn

severity and tree size/dbh, but not by tree species (PERMANOVA, Table 1, Fig 4f, i). There

was significant nestedness-driven composition dissimilarity between high severity burns

and both low- and moderate-severity burns (Fig 4f and Fig. 5j); and between small-sized

trees (Db1) and large-sized trees (Db3 and Db4) (Fig 4i; Fig 5k). In addition, there was a

significant difference in the within-class dissimilarity for burn severity; β

nes

was higher for

the high-severity burns and moderate-severity burns than in the low-severity burn class

(PERMDISP; Table 2, Fig 4f and Fig 5j). Finally, although PERMIDISP indicated a non-

significant result for tree species, the MRM analysis indicated that the nestedness-driven

dissimilarity was higher within black spruce than jack pine (Fig. 5i), which was opposite to

that observed for turnover component (Fig. 5e).

Research in Biodiversity – Models and Applications

Fig. 5. A simultaneous analysis of beta diversity patterns (β

sor

, β

sim

, β

nes

) differences within-

(gray bars) and between-habitat (black bars) classes according tree species (a,e,i), burn

severity (b,f,j), tree-size class (c, g, k) and burns (d, h, i) on saproxylic beetle’s total beta

diversity(a-d), and when partitioned into “spatial” turnover (e-h) and nestedness-driven (i-l)

components. On the y-axis are mean values of dissimilarity (beta diversity) for the

corresponding habitat contrasts. Habitat codes are as in Fig. 4.

The effects of burn severity and tree size gradients on the nestedness component of beta

diversity indicate that hierarchical suitability of the attributes is causing richness-driven

composition differences between respective treatments. Generally, large trees of low burn

severity are more suitable to saproxylic beetles than small trees of high burn severity,

because they provide suitable oviposition conditions and high quality food resources (i.e.,

subcortical tissues) for larvae feeding directly on the bark and wood of trees (Allison et al.,

2004; Saint-Germain et al., 2004). Indirectly, these trees may also be more suitable to

predators of these larvae (Kenis et al., 2004). Indeed, large-sized and/or less severly burned

treess have been shown to support more saproxylic beetle species than small-sized and/or

very severely burned trees (Azeria et al., 2010; Boulanger et al., 2010). It is interesting, and

counter intuitive, that a similar trend was also observed in the within-class nestedness-driven

composition dissimilarity among burn severity classes; thus, nestedness-driven dissimilarity

was higher for high-severity than low-severity burns. This might be explained by the high

Towards a Better Understanding of Beta Diversity: Deconstructing

Composition Patterns of Saproxylic Beetles Breeding in Recently Burnt Boreal Forest

variance (relative to average) in species richness exhibited within severe burns. We suspect

that an interaction effect between burn severity and tree-size might play a role, but this is

difficult to isolate statistically from their independent effects in PERMDISP analysis.

The above results clearly underscore that the turnover and nestedness components of

saproxylic beetles are driven by different post-fire habitat legacies. Disentangling causal

factors influencing beta diversity patterns of saproxylic beetles can have important

conservation implications, such as in post-fire salvage logging operations where

maintaining saproxylic diversity can concern management plans. Indeed, concern over

ecological consequence of post-fire salvage logging on biodiversity and ecosystem function

is a pressing management issue (Lindenmayer et al., 2008), and saproxylic beetles constitute

key component of burned forest ecosystems (Grove, 2002; Cobb et al., 2010). Knowledge

about the factors influencing beta divesity components can be crucial in setting salvage

logging practices that will conserve also these essential groups. For example, given the

species composition turnover exhibited between jack pine and black spruce, conserving the

totality of saproxylic beetle species will require a management approach that maintains a

mosaic of both tree species in the landscape. In addition, higher turnover within-jack pine

than black spruce (and within moderate severity burns) may require special considerations

to conserve all species occupying that habitat. On the other hand, the nestedness driven

component will perhaps require emphasis on habitat attributes that increase species

richness, e.g., large trees of lower severity burns. These decisions could also have

implications for the structure of forest stands that are to be set aside for protective purposes.

For example, in old-growth stands with numerous large-diameter trees (e.g., Db4=20-24), a

smaller number of trees might suffice to capture the totality of species given the low

differentiation of both turnover and nestedness component of beta diversity within large

trees (given all other attributes are considered). However, if the available forest stands

contain only moderately sized trees (e.g., Db2=12-16), then protecting more trees during

salvage-logging might be required (given high turnover), although variation of nestedness-

driven beta diversity was to the same extent as that of larger trees. These examples are just

to illustrate the implication of disentangling the turnover and nestedness components and

underlying factors for management (also see Azeria et al., 2006; 2009b; Baselga, 2010).

5. Conclusion

Ecologists face a continuing challenge to disentangle and explain the species ‘turnover’ from

composition dissimilarity that is driven by variation in species richness among sites. The

recently proposed beta diversity partitioning framework and null model approaches make a

significant step forward in meeting this challenge. We demonstrate the explicit quantitative

relationship of the beta diversity components as depicted in the partitioning framework with

that expected under and beyond random assembly of communities by using null models. Our

results indicate that the turnover component indeed reflects the beta diversity deviating beyond

that expected from “random” assembly given species richness variations, while the nestedness

component of beta diversity was related to the null expectations. In addition, the beta diversity

components were conditioned by variation in species frequency; this also implies that null

models for beta diversity studies should perhaps preserve both the observed richness and

species frequency patterns. We concur with others (Baselga 2010, Anderson et al. 2011) that the

distinction between the two beta diversity components is important, because they were driven

by different underlying causes (habitat factors) and this has implications for post-fire

management in the boreal forest. Additional studies that directly incorporate habitat and

Research in Biodiversity – Models and Applications

spatial effects into null model analysis such as using habitat- and spatially-constrained null

models are needed in order to increase our understanding of the factors that control beta

diversity patterns across space (also see Chase et al., 2011).

6. Acknowledgements

We thank Chantiers Chibougamau and Barrette Chapais Ltée for logistical support, and all

of our field assistants that helped in conducting the field work and in sample sorting. We

are indebted to Y. Dubuc and G. Pelletier for specimen identification. We thank J. Hodson

for his comments and revising the English. This study was supported by the Fonds de

recherche sur la nature et les technologies and the Ministère des Ressources naturelles et de la Faune

through the Programme de recherche en partenariat sur l’aménagement et l’environnement

forestiers-II, by the iFor consortium (Université Laval), by Environment Canada, by the

Canadian Forest Service, and by la Fondation de l’Université du Québec à Chicoutimi.

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Towards a Better Understanding of Beta Diversity: Deconstructing

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Part 2

History of Biodiversity

Twenty Landmark Papers in

Biodiversity Conservation

Corey J. A. Bradshaw

1,2

, Navjot S. Sodhi

3†

William F. Laurance

4,5

and Barry W. Brook

The Environment Institute and School of Earth and Environmental Sciences,

University of Adelaide, Adelaide,

South Australian Research and Development Institute,

Department of Biological Sciences, National University of Singapore,

School of Marine and Tropical Biology, James Cook University, Cairns,

Smithsonian Tropical Research Institute, Balboa, Ancón

1,2,4

Australia

Republic of Singapore

Panama

1. Introduction

Biodiversity conservation was first defined as a science less than three decades ago (Meine,

2010), but is now a well-developed, multidisciplinary research endeavour (Sodhi & Ehrlich,

2010). The consolidation of this ‘crisis’ field (Soulé, 1985) is inextricably tied to mounting

global environmental degradation as the human enterprise now threatens most of the

world’s biodiversity and the ecosystems of which they are part (Ehrlich & Pringle, 2008).

Although the history of the field is complex and its maturation gradual (Meine, 2010; Meine

et al., 2006), a modest number of key ideas have subsequently sparked enormous progress in

our understanding of biodiversity’s response to human impacts, and how such knowledge

might help avoid extinctions.

As the planet’s biotic crisis escalates, we reflect on some of the most important research

discoveries in biodiversity conservation science and its progenitor disciplines. Although this

is a subjective list, our rationale was to select 20 papers that either built new paradigms or

tore down old ones, and set thinking along new and interesting pathways towards

biodiversity conservation. Other authors would no doubt list different papers, or challenge

the true origin of certain ideas we highlight. Our goal here is simply to stimulate

biodiversity scientists to think about what serious innovation looks like—with the benefit of

perfect hindsight—and to use this retrospective to help guide future thinking.

In the remainder of this chapter, we briefly assess these 20 papers, but make no attempt to

rank their relative importance – apart from a citation analysis (Fig. 1). Although we do not

consider scientific citations alone reflect a paper’s value sufficiently, it does provide a simple

indication of its influence on research directions. Indeed, many of the highlighted papers

have proposed ideas that have subsequently been discredited or rendered obsolete. This is a

natural part of the progression of science. There is nonetheless little doubt that each of these

Research in Biodiversity – Models and Applications

papers has inspired new research paths and directed conservation interventions that have

arguably benefited biodiversity.

1930 1950 1970 1980 1990 2000 2010

Allee effectAllee

island biogeography

MacArthur & Wilson

tragedy of the commons

Hardin

minimum viable population size

Shaffer

ecosystem services

Ehrlich & Mooney

evil quartet | fragmentation

Diamond | Wilcox & Murphy

mesopredator release | demography vs genetics

Soulé et al. | Lande

Red List

Mace & Lande

ecological triage

Walker

declining vs small pop paradigm | extinction debt

Caughley | Tilman et al.

:N | shifting baselines

Frankham | Pauly

fishing down the web

Pauly et al.

invasional meltdown

Simberloff & Van Holle

biodiversity hotspots

Myers et al.

extinction risk from climate change

Thomas et al.

extinction synergies

Brook et al.

Fig. 1. Time line of the 20 landmark biodiversity conservation papers.

2. Landmark papers

2.1 Allee effect (Allee, 1931)

The ‘Allee effect’ can be broadly defined as a “…positive relationship between any

component of individual fitness and either numbers or density of conspecifics” (Stephens et

al., 1999). The idea is attributed to Warder Clyde Allee, an American ecologist from the early

half of the 20

Century, although Odum (1953) first named it “Allee’s principle”. We

consider Allee’s 1931 book (Allee, 1931) to be the classic source (Fig. 2). Allee discussed the

evidence for the effects of crowding on demographic and life history traits of populations,

which he subsequently redefined as “inverse density dependence” (Allee, 1941).

Broadly speaking, when populations become small, a range of positive feedbacks can reduce

a population’s average fitness (measured in many ways, such as survival probability,

reproductive rate, or growth rate). The many types of Allee effects (see Berec et al., 2007) can

be mutually reinforcing (synergistic), and so drive populations even faster toward extinction

than expected by their additive effects (Brook et al., 2008). Thus, ignoring potential Allee

effects can compromise everything from estimates of minimum viable population size

(Paper 4) to restoration attempts and predictions of extinction risk (Gregory et al., 2010).

Pavlinov I.Ya. (ed.) Research in Biodiversity - Models and Applications

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